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Simulation of Tensile Behavior of Nickel Foam

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稀有金属材料与工程 2011年第S3期40卷 224-227页

作者： Zhao Mingjuan 1, Zhang Xiaolan 1, Zhao Longzhi 1,3, Zhang Jinsong 2 1 key laboratory of ministry of education for Conveyance and Equipment, East china Jiaotong university, Nanchang 330013, china 2 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, china 3 key laboratory of Superlight materials & Surface Technology, ministry of education, Harbin Engineering university, Harbin 150001, china E china Jiaotong Univ Key Lab Minist Educ Conveyance & Equipment Nanchang 330013 Peoples R China Harbin Engn Univ Minist Educ Key Lab Supertight Mat & Surface Technol Harbin 150001 Peoples R China Chinese Acad Sci Inst Met Res Shenyang 110016 Peoples R China

Nickel foam is widely used as the electrode, the catalyst carrier, sound absorption material and other application fields. The tensile behavior of the open cell nickel foam which is one of the most important parameters in the design process was investigated with the finite element method based on ANSYS software in this paper. The effects of strain rates and temperature on the yield strength of the nickel foam were obtained. The results show that the yield strength exhibit a nonlinear reduction with the increases of the temperature for the elastic bending of the struts of the reinforcement grew quickly depending on the temperature. However, the yield strength increases slowly with the improvement of the strain rate because the strain rate neither change the internal structure and properties such as the porosity and the aperture, nor alter the external circumstance in order to change the internal properties such as the temperature. The results of the simulation accord with those of the experiments, which is very important to understand the tensile behavior of the foam materials.

关键词： nickel foam ANSYS yield strength temperature strain rate

Impacts of permafrost changes on alpine ecosystem in Qinghai-Tibet Plateau

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Science china Earth Sciences 2006年第11期49卷 1156-1169页

作者： WANG Genxu1,3 , LI Yuanshou2 , WU Qingbai2 & WANG Yibo3 1. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, china 2. Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, lanzhou 730000, china 3. Resource and Environment School, lanzhou university, lanzhou 730000, china Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu China Resource and Environment School Lanzhou University Lanzhou China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China

Alpine cold ecosystem with permafrost environment is quite sensitive to climatic changes and the changes in permafrost can significantly affect the alpine ecosystem. The vegetation coverage, grassland biomass and soil nutrient and texture are selected to indicate the regime of alpine cold ecosystems in the Qinghai-Tibet Plateau. The interactions between alpine ecosystem and permafrost were investigated with the depth of active layer, permafrost thickness and mean annual ground temperature (MAGTs). Based on the statistics model of GPTR for MAGTs and annual air temperatures, an analysis method was developed to analyze the impacts of permafrost changes on the alpine ecosystems. Under the climate change and human engineering activities, the permafrost change and its impacts on alpine ecosystems in the permafrost region between the Kunlun Mountains and the Tanggula Range of Qinghai-Tibet Plateau are studied in this paper. The results showed that the per- mafrost changes have a different influence on different alpine ecosystems. With the increase in the thickness of active layer, the vegetation cover and biomass of the alpine cold meadow exhibit a significant conic reduction, the soil organic matter content of the alpine cold meadow ecosystem shows an exponential decrease, and the surface soil materials become coarse and gravelly. The alpine cold steppe ecosystem, however, seems to have a relatively weak relation to the permafrost environment. Those relationships resulted in the fact that the distribution area of alpine cold meadow decreased by 7.98% and alpine cold swamp decreased by 28.11% under the permafrost environment degradation during recent 15 years. In the future 50 years the alpine cold meadow ecosystems in different geomorphologic units may have different responses to the changes of the permafrost under different climate warming conditions, among them the alpine cold meadow and swamp ecosystem located in the low mountain and plateau area will have a relatively

关键词： permafrost environment, alpine cold ecosystem, statistics relationship, climate change, impacts, Qinghai-Tibet Plateau.

Structure, spin reorientation and Mssbauer effect studies of Tb0.3Dy0.7(Fe1-xAlx)1.95 alloys

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Science china(Physics,Mechanics & Astronomy) 2006年第2期Mechanics & Astronomy) .卷 149-157页

作者： ZHENG Xiaoping1,2,4, ZHANG Peifeng1,3, FAN Duowang1, LI Fashen3 & HAO Yuan41. key laboratory of Opto-Electronic Technology and Intelligent Control, ministry of education, lanzhou Jiaotong university, lanzhou 730070, china 2. Institute of Electronic Information Science and Technology,lanzhou Teachers College, lanzhou 730070, china 3. key laboratory for magnetism and magnetic materials, ministry of education, lanzhou university, Lan-zhou 730000, china 4. State key Lab. of Advanced Non-Ferrous materials, Gansu Province, lanzhou university of Technology, lanzhou 730050, china

The effect of Al substitution for Fe on crystal structure, magnetostriction and spontaneous magnetostriction, anisotropy and spin reorientation of a series of polycrys-talline Tb0.3Dy0.7(Fe1?xAlx)1.95 alloys (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35) at room temperature and 77 K was investigated systematically. It was found that the primary phase of Tb0.3Dy0.7(Fe1?xAlx)1.95 is the MgCu2-type cubic Laves phase structure when x magnetic field (H ≤ 40 kA/m), but decreases sharply and is easily close to saturation in a high applied field as x increases, showing that a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. It was also found that the spontaneous magnetostriction λ111 decreases greatly with x in-creasing. The analysis of the M?ssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the changes of composition and temperature, namely spin reorientation. A small amount of non-magnetic phase exists for x = 0.15 in Tb0.3Dy0.7(Fe1?xAlx)1.95 alloys and the alloys be-come paramagnetic for x > 0.15 at room temperture, but at 77 K the alloys still remain magnetic phase even for x = 0.2. At room temperature and 77 K, the hyperfine field de-creases and the isomer shifts increase with Al concentration increasing.

关键词： magnetostriction cubic Laves phase spin reorientation M?ssbauer.

Microstructure and Tensile Properties of ZK60 Alloy Fabricated by Simplified Rapid Solidification Powder Metallurgy (S-RS P/M) Process

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Journal of materials Science & Technology 2010年第2期26卷 151-155页

作者： Zhenya Zhang, Huashun Yu , Shaoqing Wang, Haitao Wang and Guanghui Min key laboratory of Liquid Structure and Heredity of materials, ministry of education, Shandong university, Jinan 250061, china key laboratory of Liquid Structure and Heredity of materials Ministry of Education Shandong University Jinan 250061 China

This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy （RS P/M） processing system （S-RS P/M）, which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of ~1 #m in width. TEM （transmission electron microscopy） observations illustrated nano-size magnesia particles （10-30 nm） constituted oxide stringer in detail. Due to a relatively higher volume of nano-size magnesia particle produced during S-RS P/M process, 0.2% yield strength of S-RS P/M ZKO0 alloy was found to be as high as 382 MPa, which is 10% higher than that of RS P/M alloy. The improvement in mechanical properties is mainly attributed to the combination effects of Orowan mechanism and coefficient of thermal expansion （CTE） mismatch because of the approximately same average grain size.

关键词： Microstructure Mechanical properties Rapid solidification powder metallurgy Nano-size magnesia

Preparation and Characterization of ZrO_2 Nanoparticles Capped by Trioctylphosphine Oxide (TOPO)

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Journal of Wuhan university of Technology(materials Science) 2011年第4期26卷 611-614页

作者：马剑琪 School of Chemistry and Environmental Science Shaanxi University of Technology State key laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences

Monodisperse ZrO2 nanoparticles capped by trioctylphosphine oxide （TOPO） were prepared in non-aqueous solvent using in-situ synthesis method. Transmission electron microscopy（TEM）, X-ray diffraction（XRD）, X-ray photoelectron spectrometer（XPS）, Fourier transformation infrared spectroscopy （FTIR）, and thermogravimetric analysis（TGA） were adopted to characterize and investigate the size, structure, composition, and the binding manners between organic capping agent TOPO and inorganic ZrO2 nanocores of the as-prepared nanoparticles. In addition, the nanoparticles were also studied to determine their solubility and relative stability. The experimental results show that the prepared nanoparticles contain about 25% organic capping shell TOPO, 75% inorganic ZrO2 nanocores, and can be easily dissolved and be stably disersed in non-polar organic solvents.

关键词： ZrO2 nanoparticles trioctylphosphine oxide (TOPO) monodisperse solubility

Effects of surface modification on isothermal oxidation behavior of HVOF-sprayed NiCrA1Y coatings

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Progress in Natural Science:materials International 2011年第2期21卷 173-179页

作者： Li-yong NI,Zi-long WU,Chun-gen ZHOU key laboratory of Aerospace materials and Performance(ministry of education), Department of materials Science and Engineering,Beihang university,Beijing 100191,china key laboratory of Aerospace materials and Performance (ministry of education) Department of Materials Science and Engineering Beihang University Beijing 100191 China

NiCrAlY coatings were deposited on Ni-based superalloy by high-velocity oxygen-fuel spraying(HVOF).Surface modification by means of grit-blasted,shot-peened and ground methods was used in order to study the effect of surface conditions on the isothermal oxidation behavior of HVOF-sprayed NiCrAlY coatings at 1 050℃.The results showed that surface modification had an obvious effect on the isothermal oxidation behavior of the *** was a large decrease in growth rate compared with the as-sprayed *** scale formed on the grit-blasted and shot-peened coatings was a mixture of Al2O3and NiCr2O4,while the oxide formed on the ground coating was composed mainly of *** surface modification,the content of NiCr2O4spinels decreased compared with the as-sprayed coating.

关键词： NiCrAlY HVOF isothermal oxidation thermal barrier coating

Microstructures and corrosion properties of casting in situ Al_3Ti-Al composites

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Rare Metals 2010年第1期29卷 78-85页

作者： CHEN Tijun LI Jian HAO Yuan Gansu key laboratory of Advanced Nonferrous materials Lanzhou University of Technology Lanzhou 730050 China School of Material Science and Engineering Xi＇an Shiyou University Xi ＇an 710065 China

The effects of Ti content and the alloying elements of Si and Cu on the microstructures of casting in situ Al3Ti-Al composites were investigated. Simultaneously, their corrosion properties were also discussed. The results indicate that the aspect ratios of Al3Ti platelets in different Al based composites are different although all of them are in flaky shape. The morphologies of Al3Ti phase are not only determined by Ti content, but are also related to the alloying elements. The grain refining role of Al3Ti phase in the pure Al and Al-Cu based composites is more effective than that in the Al-Si based composite. The addition of Ti decreases the corrosion resistance of pure Al and Al alloys. The corrosion resistances of the composites are dependent on both the corrosion characteristics of the corresponding matrixes and the distribution of Al3Ti platelets.

关键词： metal matrix composite microstructure corrosion resistance alloying element morphology

Effects of solidification parameters on microstructure and mechanical properties of continuous columnar-grained Cu-Al-Ni alloy

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Progress in Natural Science:materials International 2011年第5期21卷 368-374页

作者： Zhen WANG,Xue-feng LIU,Jian-xin XIE key laboratory for Advanced materials Processing,ministry of education, university of Science and Technology Beijing,Beijing 100083,china key laboratory for Advanced materials Processing Ministry of Education University of Science and Technology Beijing Beijing 100083 China

Effects of melt temperature and casting speed on microstructure and mechanical properties of Cu-14%Al-3.8%Ni(mass fraction) alloy wires fabricated by continuous unidirectional solidification technology were *** was found that the average size of columnar grain in the alloy decreased and grain boundary turned clear and straight with increasing the casting speed at a given melt *** the melt temperature was up to 1 280℃,theβ1phase gradually transformed into lozenged and lanciformγ’1martensite,as well as parallel-sided plateβ’*** alloy with numerous coarsely dendriticγ2phase has poor mechanical properties due to the difficulty of stress-induced martensitic *** the amount of theγ2phase reduced and the coarse dendriteγ2phase evolved into the fine square particles,the elongation of the alloy increased gradually with a decrease in tensile ***,the plasticity of the alloy could also be improved by increasing the amount and size of martensites,particularly the lanciformγ’*** the alloy was almost composed of coarse lanciformγ’1martensite,the tensile strength and elongation of the alloy could be up to 772 MPa and 18.9%,respectively,and the tensile curve consisted of three transformation platforms.

关键词： shape memory alloy continuous unidirectional solidification columnar grain martensitic transformation

ULTRASONIC SEPARATION OF MICRO-SIZED INCLUSIONS IN MOLTEN METAL

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Acta Metallurgica Sinica(English Letters) 2001年第5期14卷 375-379页

作者： X.Q. Bai and J.C. He key laboratory of National education ministry for Electromagnetic Processing of materials, Northeastern university, Shenyang 110004, china Northeastern Univ. Shenyang 110004 China

The coagulation time and position of micro-sized non-metallic inclusions in molten metal during ultrasonic separation process were investigated, and the motion course of micro-sized non-metallic inclusions in an ultrasonic standing wave field was numerically simulated. The results of theoretical analysis and numerical simulation show that the movement of inclusions depends on the balance between the acoustic radiation force, effective buoyancy force and viscous drag force. It is presented that micro-sized inclusions, agglomerated at antinode-planes may be removed further with horizon tal ultrasound.``

关键词： ultrasound molten metal micro-sized non-metallic inclusion numerical simulation process parameter